Consolidated Statement of Changes in Equity - USD ($) $ in Millions	Total	Cumulative effect, period of adoption, adjustment	Total	Common Shares	Common Stock and Capital Surplus	Retained Earnings	Retained Earnings Cumulative effect, period of adoption, adjustment	Accumulated Other Comprehensive Inc. (Loss)	Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 4,972		$ 4,970		$ 1,334	$ 3,588		$ 48	$ 2
Beginning Balance, shares at Dec. 31, 2018				89,291,724
Beginning Balance at Dec. 31, 2018	4,972		4,970		1,334	3,588		48	2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to parent	897		897			897
Net income (loss), including portion attributable to nonredeemable noncontrolling interest	895								(2)
Other comprehensive income (loss)	815		815					815	0
Other comprehensive income (loss), including portion attributable to noncontrolling interest	815
Dividends	(446)		(446)			(446)
Shares issued:
Exercise of stock options, shares				747,167
Exercise of stock options	31		31		31
Restricted stock awards, shares				232,635
Restricted stock awards	0		0		0
Other benefit plans, shares				77,429
Other benefit plans	8		8		8
Dividend reinvestment plan, shares				19,334
Dividend reinvestment plan	2		2		2
Stock-based compensation expense	23		23		23
Shares exchanged — benefit plans, shares				(50,062)
Shares exchanged — benefit plans	(5)		(5)		(1)	(4)
Forfeitures of restricted stock, shares				(14,541)
Forfeitures of restricted stock	0		0		0
Other	(26)		(26)			(26)			0
Ending Balance, shares at Dec. 31, 2019				90,303,686
Ending Balance at Dec. 31, 2019	6,269	$ 7	6,269		1,397	4,009	$ 7	863	0
Beginning Balance, redeemable noncontrolling interests at Dec. 31, 2018	0
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Net income (loss) attributable to redeemable noncontrolling interest	(26)
Other	26
Ending Balance, redeemable noncontrolling interests at Dec. 31, 2019	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	6,269	$ 7	6,269		1,397	4,009	$ 7	863	0
Net income (loss) attributable to parent	732		732			732
Net income (loss), including portion attributable to nonredeemable noncontrolling interest	734								2
Other comprehensive income (loss)	416		414					414	0
Other comprehensive income (loss), including portion attributable to noncontrolling interest	414
Dividends	(336)		(336)			(336)
Shares issued:
Exercise of stock options, shares				328,471
Exercise of stock options	14		14		14
Restricted stock awards, shares				227,867
Restricted stock awards	0		0		0
Other benefit plans, shares				143,270
Other benefit plans	10		10		10
Dividend reinvestment plan, shares				18,690
Dividend reinvestment plan	2		2		2
Stock-based compensation expense	20		20		20
Shares acquired and retired, shares				(4,531,394)
Shares acquired and retired	(313)		(313)		(70)	(243)
Shares exchanged — benefit plans, shares				(101,663)
Shares exchanged — benefit plans	(11)		(11)		(2)	(9)
Forfeitures of restricted stock, shares				(43,681)
Forfeitures of restricted stock	0		0		0
Other	$ (21)		(19)		(4)	(11)		(4)	(2)
Ending Balance, shares at Dec. 31, 2020	86,345,246			86,345,246
Ending Balance at Dec. 31, 2020	$ 6,789		6,789		1,367	4,149		1,273	0
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Net income (loss) attributable to redeemable noncontrolling interest	(13)
Other comprehensive income (loss), net of tax attributable to redeemable noncontrolling interests	2
Other	11
Ending Balance, redeemable noncontrolling interests at Dec. 31, 2020	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	6,789		6,789		1,367	4,149		1,273	0
Net income (loss) attributable to parent	1,995		1,995			1,995
Net income (loss), including portion attributable to nonredeemable noncontrolling interest	1,995								0
Other comprehensive income (loss)	(1,154)		(1,154)					(1,154)	0
Other comprehensive income (loss), including portion attributable to noncontrolling interest	(1,154)
Dividends	$ (2,382)		(2,382)			(2,382)
Shares issued:
Exercise of stock options, shares	1,208,964			1,208,964
Exercise of stock options	$ 59		59		59
Restricted stock awards, shares				207,020
Restricted stock awards	0		0		0
Other benefit plans, shares				81,286
Other benefit plans	10		10		10
Dividend reinvestment plan, shares				69,095
Dividend reinvestment plan	8		8		8
Stock-based compensation expense	16		16		16
Shares acquired and retired, shares				(2,777,684)
Shares acquired and retired	(319)		(319)		(44)	(275)
Shares exchanged — benefit plans, shares				(92,209)
Shares exchanged — benefit plans	(10)		(10)		(1)	(9)
Forfeitures of restricted stock, shares				(120,753)
Forfeitures of restricted stock	$ 0		0		0
Ending Balance, shares at Dec. 31, 2021	84,920,965			84,920,965
Ending Balance at Dec. 31, 2021	$ 5,012		5,012		1,415	3,478		119	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 5,012		$ 5,012		$ 1,415	$ 3,478		$ 119	$ 0